全文获取类型
收费全文 | 676篇 |
免费 | 54篇 |
国内免费 | 4篇 |
专业分类
734篇 |
出版年
2022年 | 7篇 |
2021年 | 5篇 |
2020年 | 5篇 |
2019年 | 7篇 |
2018年 | 15篇 |
2017年 | 16篇 |
2016年 | 25篇 |
2015年 | 25篇 |
2014年 | 39篇 |
2013年 | 41篇 |
2012年 | 82篇 |
2011年 | 95篇 |
2010年 | 49篇 |
2009年 | 30篇 |
2008年 | 22篇 |
2007年 | 23篇 |
2006年 | 22篇 |
2005年 | 22篇 |
2004年 | 16篇 |
2003年 | 22篇 |
2002年 | 12篇 |
2001年 | 10篇 |
2000年 | 6篇 |
1999年 | 10篇 |
1998年 | 7篇 |
1997年 | 4篇 |
1996年 | 8篇 |
1995年 | 11篇 |
1994年 | 7篇 |
1993年 | 3篇 |
1992年 | 8篇 |
1991年 | 8篇 |
1990年 | 4篇 |
1989年 | 2篇 |
1988年 | 6篇 |
1987年 | 3篇 |
1986年 | 10篇 |
1985年 | 5篇 |
1983年 | 5篇 |
1982年 | 3篇 |
1978年 | 6篇 |
1977年 | 4篇 |
1976年 | 4篇 |
1975年 | 6篇 |
1973年 | 2篇 |
1972年 | 2篇 |
1970年 | 1篇 |
1969年 | 1篇 |
1967年 | 1篇 |
1966年 | 1篇 |
排序方式: 共有734条查询结果,搜索用时 15 毫秒
81.
Adult stem cells are responsible for the cellular turnover of many organs, and an impairment in their function leads to aging and disease. In efforts to reverse the process of tissue stem cell aging, we speculate on the promise and challenges of in vivo direct reprogramming strategies. 相似文献
82.
I Anderson E Saunders A Lapidus M Nolan S Lucas H Tice TG Del Rio JF Cheng C Han R Tapia LA Goodwin S Pitluck K Liolios K Mavromatis I Pagani N Ivanova N Mikhailova A Pati A Chen K Palaniappan M Land L Hauser CD Jeffries YJ Chang EM Brambilla M Rohde S Spring M Göker JC Detter T Woyke J Bristow JA Eisen V Markowitz P Hugenholtz NC Kyrpides HP Klenk 《Standards in genomic sciences》2012,6(2):155-164
Thermodesulfatator indicus Moussard et al. 2004 is a member of the Thermodesulfobacteriaceae, a family in the phylum Thermodesulfobacteria that is currently poorly characterized at the genome level. Members of this phylum are of interest because they represent a distinct, deep-branching, Gram-negative lineage. T. indicus is an anaerobic, thermophilic, chemolithoautotrophic sulfate reducer isolated from a deep-sea hydrothermal vent. Here we describe the features of this organism, together with the complete genome sequence, and annotation. The 2,322,224 bp long chromosome with its 2,233 protein-coding and 58 RNA genes is a part of the Genomic Encyclopedia of Bacteria and Archaea project. 相似文献
83.
B Abt C Han C Scheuner M Lu A Lapidus M Nolan S Lucas N Hammon S Deshpande JF Cheng R Tapia LA Goodwin S Pitluck K Liolios I Pagani N Ivanova K Mavromatis N Mikhailova M Huntemann A Pati A Chen K Palaniappan M Land L Hauser EM Brambilla M Rohde S Spring S Gronow M Göker T Woyke J Bristow JA Eisen V Markowitz P Hugenholtz NC Kyrpides HP Klenk JC Detter 《Standards in genomic sciences》2012,6(2):194-209
Spirochaeta coccoides Dröge et al. 2006 is a member of the genus Spirochaeta Ehrenberg 1835, one of the oldest named genera within the Bacteria. S. coccoides is an obligately anaerobic, Gram-negative, non-motile, spherical bacterium that was isolated from the hindgut contents of the termite Neotermes castaneus. The species is of interest because it may play an important role in the digestion of breakdown products from cellulose and hemicellulose in the termite gut. Here we provide a taxonomic re-evaluation for strain SPN1T, and based on physiological and genomic characteristics, we propose its reclassification as a novel species in the genus Sphaerochaeta, a recently published sister group of the Spirochaeta. The 2,227,296 bp long genome of strain SPN1T with its 1,866 protein-coding and 58 RNA genes is a part of the Genomic
Encyclopedia of
Bacteria and
Archaea project. 相似文献
84.
Sandra López Beatriz Lima Liliana Aragón Luis Ariza Espinar Alejandro Tapia Susana Zacchino Julio Zygadlo Gabriela Egly Feresin María Liza López 《化学与生物多样性》2012,9(8):1452-1464
The essential oils (EOs) of two populations of Azorella cryptantha (Clos) Reiche , a native species from San Juan Province, were obtained by hydrodistillation in a Clevenger‐type apparatus and characterized by GC‐FID and GC/MS analyses. The compounds identified amounted to 92.3 and 88.7% of the total oil composition for A. cryptantha from Bauchaceta (Ac‐BAU) and Agua Negra (Ac‐AN), respectively. The EO composition for the two populations was similar, although with differences in the identity and content of the main compounds and also in the identity of minor components. The main compounds of the Ac‐BAU EO were α‐pinene, α‐thujene, sabinene, δ‐cadinene, δ‐cadinol, trans‐β‐guaiene, and τ‐muurolol, while α‐pinene, α‐thujene, β‐pinene, γ‐cadinene, τ‐cadinol, δ‐cadinene, τ‐muurolol, and a not identified compound were the main constituents of the Ac‐AN EO, which also contained 3.0% of oxygenated monoterpenes. The repellent activity on Triatoma infestans nymphs was 100 and 92% for the Ac‐AN and Ac‐BAU EOs, respectively. Regarding the toxic effects on Ceratitis capitata, the EOs were very active with LD50 values lower than 11 μg/fly. The dermatophytes Microsporum gypseum, Trichophyton rubrum, and T. mentagrophytes and the bacterial strains Escherichia coli LM1, E. coli LM2, and Yersinia enterocolitica PI were more sensitive toward the Ac‐AN EO (MIC 125 μg/ml) than toward the Ac‐BAU EO. This is the first report on the composition of A. cryptantha EO and its anti‐insect and antimicrobial properties. 相似文献
85.
86.
Lauren A. V. Orenstein Evan W. Orenstein Ibrahima Teguete Mamoudou Kodio Milagritos Tapia Samba O. Sow Myron M. Levine 《PloS one》2012,7(10)
Background
Maternal immunization has gained traction as a strategy to diminish maternal and young infant mortality attributable to infectious diseases. Background rates of adverse pregnancy outcomes are crucial to interpret results of clinical trials in Sub-Saharan Africa.Methods
We developed a mathematical model that calculates a clinical trial''s expected number of neonatal and maternal deaths at an interim safety assessment based on the person-time observed during different risk windows. This model was compared to crude multiplication of the maternal mortality ratio and neonatal mortality rate by the number of live births. Systematic reviews of severe acute maternal morbidity (SAMM), low birth weight (LBW), prematurity, and major congenital malformations (MCM) in Sub-Saharan African countries were also performed.Findings
Accounting for the person-time observed during different risk periods yields lower, more conservative estimates of expected maternal and neonatal deaths, particularly at an interim safety evaluation soon after a large number of deliveries. Median incidence of SAMM in 16 reports was 40.7 (IQR: 10.6–73.3) per 1,000 total births, and the most common causes were hemorrhage (34%), dystocia (22%), and severe hypertensive disorders of pregnancy (22%). Proportions of liveborn infants who were LBW (median 13.3%, IQR: 9.9–16.4) or premature (median 15.4%, IQR: 10.6–19.1) were similar across geographic region, study design, and institutional setting. The median incidence of MCM per 1,000 live births was 14.4 (IQR: 5.5–17.6), with the musculoskeletal system comprising 30%.Interpretation
Some clinical trials assessing whether maternal immunization can improve pregnancy and young infant outcomes in the developing world have made ethics-based decisions not to use a pure placebo control. Consequently, reliable background rates of adverse pregnancy outcomes are necessary to distinguish between vaccine benefits and safety concerns. Local studies that quantify population-based background rates of adverse pregnancy outcomes will improve safety assessment of interventions during pregnancy. 相似文献87.
Rodrigo Valenzuela Alejandra Espinosa Daniel González-Ma?án Amanda D'Espessailles Virginia Fernández Luis A. Videla Gladys Tapia 《PloS one》2012,7(10)
Omega-3 (n-3) long-chain polyunsaturated fatty acids (n-3 LCPUFA) are associated with several physiological functions, suggesting that their administration may prevent non transmissible chronic diseases. Therefore, we investigate whether dietary n-3 LCPUFA supplementation triggers an antioxidant response preventing liver steatosis in mice fed a high fat diet (HFD) in relation to n-3 LCPUFA levels. Male C57BL/6J mice received (a) control diet (10% fat, 20% protein, 70% carbohydrate), (b) control diet plus n-3 LCPUFA (108 mg/kg/day eicosapentaenoic acid plus 92 mg/kg/day docosahexaenoic acid), (c) HFD (60% fat, 20% protein, 20% carbohydrate), or (d) HFD plus n-3 LCPUFA for 12 weeks. Parameters of liver steatosis, glutathione status, protein carbonylation, and fatty acid analysis were determined, concomitantly with insulin resistance and serum tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 levels. HFD significantly increased total fat and triacylglyceride contents with macrovesicular steatosis, concomitantly with higher fasting serum glucose and insulin levels, HOMA, and serum TNF-α, IL-1β, and IL-6. Reduced and total liver glutathione contents were diminished by HFD, with higher GSSG/GSH ratio and protein carbonylation, n-3 LCPUFA depletion and elevated n-6/n-3 ratio over control values. These changes were either reduced or normalized to control values in animals subjected to HFD and n-3 LCPUFA, with significant increased hepatic total n-3 LCPUFA content and reduced n-6/n-3 ratio being observed after n-3 LCPUFA supplementation alone. So, repletion of liver n-3 LCPUFA levels by n-3 LCPUFA dietary supplementation in HFD obese mice reduces hepatic lipid content, with concomitant antioxidant and anti-inflammatory responses favouring insulin sensitivity. 相似文献
88.
89.
Microdialysis perfusion of alpha-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid (AMPA) in rat lumbar spinal cord produces severe motoneuron damage and consequently hindlimb paralysis. Here we studied the time course of the AMPA-induced neurodegenerative changes and motor alterations, and the protective effect of leupeptin, an inhibitor of calpain, a Ca(2+)-activated protease. Paralysis occurs at 4-6 h after AMPA perfusion, but cresyl violet staining showed that motoneuron damage starts at about 3 h and progresses until reaching 50% neuronal loss at 6 h and 90% loss at 12 h. In contrast, choline acetyltransferase (ChAT) immunohistochemistry revealed that the enzyme is already decreased at 30 min after AMPA perfusion and practically disappears at 3 h. Microdialysis coperfusion of leupeptin with AMPA prevented the motor alterations and paralysis and remarkably reduced both the decrement in ChAT immunoreactivity and the loss of motoneurons. We conclude that an increased Ca(2+) influx through Ca(2+)-permeable AMPA receptors activates calpain, and as a consequence ChAT content decreases earlier than other Ca(2+)-dependent processes, including the proteolytic activity of calpain, cause the death of motoneurons. 相似文献
90.
Jordan Miguel Larrain Monica Tapia Andrea Roveraro Carlos 《Plant Cell, Tissue and Organ Culture》2001,66(2):89-95
Embryonic axes with cotyledons, shoot-tips of embryonic axes, isolated cotyledons, as well as axillary buds and leaves from
20-year-old trees of Sophora toromiro, were evaluated for their capacity to trigger organogenesis and to regenerate plantlets under in vitro conditions. Embryonic shoot-tips were the only explants capable of regenerating plants. They developed rapidly in vitro in the presence of NAA and BA while in subculture roots were induced at the proximal end in the presence of 0.49 μM IBA within
40–60 days. Development was completed with a subculture phase under non-sterile conditions using a mixture of equal parts
of sterilized vermiculite/sand/soil in growth chambers, before final acclimation in the greenhouse. In the presence of NAA,
BA and GA3, whole embryonic axes formed multiple shoots that branched when grown in 2.27 or 11.35 μM TDZ in subculture. Similarly, callus
was initiated at the embryo axis base, developing into several new shoots in the presence of TDZ. Because of the relatively
high shoot induction rate along the embryonic axis, this axis presents a valuable source of new juvenile explants. Growth
and rhizogenesis was satisfactory only when organs from seed pods of the year or from the previous season were used. Experiments
with isolated cotyledons produced callus only, while axillary buds and leaves did not show any responses in the presence of
several growth regulators assayed. Inoculation of seedlings with various strains of rhizobia under in vitro conditions resulted in root outgrowths, but not in nodules that are typical of rhizobia infection.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献